In a phase IIb study, patients on the investigational drug CVT-301 had a significant reduction in Unified Parkinson's Disease Rating Scale (UPDRS) Part III scores over 4 weeks compared with placebo, Robert Hauser, MD, of the University of South Florida Medical Center in Tampa, and colleagues reported in a poster at the Movement Disorders Society meeting here.

"It can serve an unmet need," Hauser told MedPage Today. "If it proves safe and effective in phase III trials, it has the potential to be helpful."

"Off" episodes involve re-emergence of motor symptoms such as an impaired ability to move, muscle stiffness, and tremor; these occur because the effectiveness of oral levodopa wanes before the next dose can safely be given. Current therapies for these episodes, which affect up to half of all patients on levodopa, are limited, the researchers said.

Since levodopa is the most effective oral treatment for Parkinson's symptoms, the ability to bridge those periods between doses could be useful, Hauser said.

For the study, the researchers randomized 86 patients with Parkinson's disease to either the investigational inhaled product or to placebo during a 4-week period. For the first 2 weeks, patients took a 35-mg dose, and for the last 2 weeks they took the 50-mg dose.

All patients were on levodopa therapy, and their mean intake was 770 mg/day, with an average "off" time of 6 hours per day.

The primary outcome was change in scores on the UPDRS Part III during "off" periods.

On average, patients used the "rescue" levodopa or placebo about two times per day.

Hauser and colleagues found that the drug significantly improved UPDRS Part III scores at all time points between 10 and 60 minutes after administration compared with placebo (P<0.05).

By the end of the 4-week study, mean change in UPDRS Part III scores were significantly better for drug patients, for both doses:

35 mg: -9.9 versus -5.3, P=0.007

50 mg: -10 versus -3.1, P<0.001

Patients also reported reductions in "off" time -- by 1.1 hours/day with the 35-mg dose, and by a significant 1.6 hours/day with the 50-mg dose.

There were more adverse events in the drug group -- 47% versus 33% -- including dizziness, cough, nausea, and anxiety, which could be tied to an excess of drug, but that would need further study, Hauser said.

They concluded that inhaled levodopa improves motor function as early as 10 minutes after administration, reduces "off" time, and appears to be safe and well tolerated.

Drugmaker Acorda Therapeutics is currently enrolling patients in a phase III trial of the drug.

Peter Jenner, MD, of King's College London, said in a statement that the novel inhaled formulation "appears to offer a further and novel route of administration of levodopa that can be used to treat 'off' periods."

"My immediate thought is that it will offer an alternative to rescue from 'off' periods currently achieved by subcutaneous injection of apomorphine," Jenner said. "A noninvasive form of rescue therapy will have utility and convenience for patients with Parkinson's disease experiencing sudden 'off' and improve their quality of life."

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